Luminescence dating of cyclone-induced washover fans at Point Lefroy (NW Australia)

Brill, Dominik; May, Simon Matthias; Shah-Hosseini, Majid; Rufer, Daniel; Schmidt, Christoph; Engel, Max (2017). Luminescence dating of cyclone-induced washover fans at Point Lefroy (NW Australia). Quaternary geochronology, 41, pp. 134-150. Elsevier 10.1016/j.quageo.2017.03.004

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Reliable age dating of coastal sedimentary landforms is crucial for inferring storm frequencies and magnitudes from geological archives. However, in highly energetic coastal settings, radiocarbon dating is often biased by reworking and/or poorly constrained marine reservoir effects. Due to this, most cyclone-driven sediment archives from the semiarid coast of NW Australia – a region frequently affected by tropical cyclones but with a historical record limited to ∼150 a, and therefore strongly in need of long-term data inferred from geological evidence – are affected by chronological inaccuracies. Optically stimulated luminescence dating (OSL) may overcome these shortcomings by dating the transport of sediment directly. In turn it may be related to other challenges when applied to cyclone deposits from semiarid environments. The cyclone-induced washover fans at Point Lefroy, NW Australia, are composed of a heterogeneous mixture of coral fragments, shell hash and siliciclastic sand. This makes them particularly prone to high dose scatter resulting from a combination of partial bleaching, sediment mixing and dose-rate heterogeneity. The washover fans are further characterised by a discontinuous nature of cyclone deposition, as indicated by erosional features and macroscopic brunification horizons. By using a combination of quartz single grain dating, autoradiography, alpha counting and gamma spectrometry, sediment mixing and dose rate heterogeneity are identified as the main sources of dose scatter. The resulting chronology allows us to discriminate at least four well constrained phases of washover fan activity at ∼180, ∼360, ∼870, and ∼1300 a ago. Older but less well constrained activity phases occurred ∼1950, ∼2300, and ∼2830 a ago. While these phases of increased cyclone activity correlate with depositional units separated by potential palaeosols, OSL ages, quasi-continuous portable OSL reader measurements and gamma spectrometry measured with increased sampling resolution point to deposition of distinct washover units within a very short period of time. However, unambiguous discrimination between deposition of individual units by single events and deposition by several cyclones within periods of only a few decades is currently not possible.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences
08 Faculty of Science > Institute of Geological Sciences > Rock-Water Interaction

UniBE Contributor:

Rufer, Daniel

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

1871-1014

Publisher:

Elsevier

Language:

English

Submitter:

Daniel Rufer

Date Deposited:

09 Nov 2017 17:50

Last Modified:

09 Nov 2017 17:50

Publisher DOI:

10.1016/j.quageo.2017.03.004

Uncontrolled Keywords:

OSL, Cyclone deposit, Washover fan, Equivalent dose scatter, Beta-dose heterogeneity, Single grain dating, Australia

BORIS DOI:

10.7892/boris.105482

URI:

https://boris.unibe.ch/id/eprint/105482

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